Future oil and gas forecasts by an economic watchdog have been described as "incredibly pessimistic" and could be six times lower than the actual levels, according to a report.

The Scottish and UK Governments have repeatedly clashed over the future of the industry, particularly around forecasts from the UK Office for Budget Responsibility (OBR) on the amount of cash it expects to be raised from the North Sea.

The Scottish Government argues the OBR forecasts are based on a ''very low estimate of future total production'', while its own figures have been criticised by opponents who claim they are overly optimistic.

In July, OBR chairman Robert Chote revealed the independent body is now forecasting revenues of £61.6 billion will be raised between 2013/14 and 2040/41 - down from £82.2 billion.

An economic report by N-56, described as an 'apolitical business organisation', said the figure could be as high as £365 billion if a series of recommendations are implemented.

Among the recommendations, some of which were highlighted by the Wood Review earlier this year, is that a more competitive tax regime is established for the North Sea, all policy and decision makers responsible for taxation and regulation of the industry be moved to Aberdeen regardless of the referendum result, the creation of a Hydrocarbon Investment Bank to boost investment and a host of technological schemes between industry to boost oil recovery.

An oil fund should also be established to ensure fiscal stability, it said.

Graeme Blackett from N-56 said: "Since 1970 over £1 trillion in oil and gas revenues have been produced by the North Sea and at least as much value remains to be produced as already has been, presenting a tremendous opportunity for the sector and for Scotland's public finances.

"Scotland is a net contributor to the UK public finances, in part due to our geographic share of oil and gas revenues, and this ensures that our finances are typically healthier than the UK public finances as whole.

"The OBR puts forward incredibly pessimistic forecasts on both barrel price and reserves, largely discredited by industry experts.

"What is clear is these natural resources can be maximised through implementing the recommendations put forward both by ourselves and the Wood Review, delivering considerable surpluses that we would recommend are used to invest in an oil fund to benefit future generations."

The report comes as it was announced that potential oil and gas discoveries off the west coast of Scotland are to be examined in a partnership between the Scottish Government, industry and academics.

Areas including the Solway Firth, the Firth of Clyde, the North Channel and the Sea of the Hebrides will be the focus of the study.

Only around 20 exploration wells have been drilled off the west coast of the mainland, compared to the thousands drilled in the north and north east of the country.

The N-56 report was welcomed by the First Minister.

Alex Salmond said: "This substantial new report from a leading business organisation blows another huge hole in the credibility of the OBR's oil forecasts, especially as it comes just days after esteemed Scottish economist, Professor Sir Donald Mackay, said the OBR's calculations were 'precisely wrong' and 'hopelessly at sea'.

"The report also endorses the Scottish Government's plans to set up an energy fund - something Westminster have consistently failed to do to the great detriment of current and future generations.

"Instead of continuing to talk down Scotland's oil and gas sector, the No campaign should acknowledge that the sector has a bright future ahead of it.

"With a Yes vote in September we will be able to ensure that the sector benefits from a more stable taxation regime instead of being subject to surprise Treasury tax grabs - maximising the jobs that the industry creates and revenue for the long-term, and ensuring that Scotland's resources are used to the full benefit of the people of Scotland."

A Treasury spokesman said: "As part of the UK every man, woman and child in Scotland is £1,400 better off.

"The Scottish Government's claim that Scotland's public finances will be boosted by separation are based on inflated oil and gas forecasts. Every independent expert agrees that North Sea oil and gas revenues are volatile and will ultimately decline. The Scottish Government's own stats show that over the past two years, North Sea tax revenues were around £5 billion less than the Scottish Government's lowest estimate.

"The North Sea is a maturing basin and it needs valuable incentives from the Exchequer to sustain investment, which the UK, with its broad and diverse tax base, is able to provide.

"An independent Scotland would have to invest almost £3,800 per head - over ten times more than when the costs are spread across the whole UK - to match the estimated £20 billion the UK Government has guaranteed to provide on decommissioning relief in the North Sea. This report takes no account of these costs.

"It is not credible for the Scottish Government to say they would sustain current tax incentives for the oil industry and set up an oil fund, while cutting corporation tax below the UK level and increasing welfare benefits.

"How would they fund all these tax cuts, ensure increase public spending and put money aside for an oil fund?"

A Better Together spokesman said: "It's not surprising that a report by an organisation founded by an advisor to Yes Scotland has reached this conclusion.

"All independent experts make clear that the tax we can expect to get from oil is declining and volatile. The broad shoulders of the UK mean we can make the most of the oil that is left without putting the money for our schools and hospitals at the mercy of volatile oil prices.

"By saying No Thanks to separation we can have the best of both worlds for Scotland - a strong Scottish Parliament, with more powers guaranteed, backed up by the strength security and stability of the United Kingdom which will protect funding for our public services."